The invention is situated in the field of the control of physical access to entrances to a sensitive area and more particularly checking the uniqueness of a person passing through a controlled passage. This field contains two types of problem, a first consisting of authenticating a person presenting himself, the second consisting of ensuring that only the authenticated person passes through the controlled passage so as to guard against fraud or an unauthorised person profiting from the passage of an authorised person in order to slip through (“tailgating” in English).
A method of detecting uniqueness in a lobby is known from the document EP 0 706 062. This method couples a ticket reader for validating a transport pass and ultrasonic detection. Only one type of sensor is used.
A method of protecting an access based on the authentication of persons by a single sensor system is known from the document US 2002/097145 A1. It is not sought to ensure uniqueness of the passage.
A method of protecting access by image analysis is known from the document WO 03/088157 A. A detection of the objects is carried out, these objects are classified, and characteristics are extracted from them in order to determine attempts at fraud.
An access control system having three different zones is known from the document FR 2 713 805. In a first so-called toll zone, the users make the payment. In a second zone, the persons are counted. In a third zone, referred to as the passing zone, a barrier may close where the number of persons counted is higher than the payment number. The aim here is to count the persons rather than to identify fraud types of fraud.
It is known from FR 2 871 602 A how to use a pressure mat on the ground for determining whether one person or more are situated on the mat and controlling the opening of a door according to the result of this test.
Systems for counting persons using an entrance by video image processing are known through the document EP 1 100 050 A1. In this document, only one type of sensor is used. It is also known through the document US 2002/0067259 A1 how to use several types of sensor to determine the presence of a person and his uniqueness. In this document, it is described how to correlate the data from several sensors, a beam cutoff configuration and a heat detector, in order to detect a non-human object so as to discriminate a person with luggage from an intrusion. As for the document US 2004/0188185, this describes correlating the information from a heat image and an optical image in order to count the number of persons present in a space. In the document EP 1 308 905 A1 a description is given of the use of a pressure-sensitive mat for detecting the presence of persons and their direction of movement, and effecting a counting from the data from the mat and their change over time.
These methods are however not sufficient to detect with reliability attempts at fraud by a determined person.